The alleged assault took place on Silver Street, near to Hallgate, at around 4am this morning.
A spokesman for the Doncaster Central Local Policing Team said: "Did you witness a serious assault?
"Anyone information call 101 and quote incident number 238 of May 29, 2016."
Police have not yet released information on the person injured, or the number of people involved in the assault.
More to follow.